The present invention relates to a stator, a motor, a method for manufacturing a conductor, and a method for manufacturing the motor.
Conventionally, various types of motors having a number of slots arranged circumferentially in a stator in correspondence with every magnetic pole of a rotor and SC (segment conductor) coils mounted in the slots have been proposed as a motor, such as a brushless motor. See, for example, Japanese Laid-Open Patent Publication No. 11-98788. In a motor described in this document, the number of slots per magnetic pole of a rotor is increased to decrease cogging torque and increase the occupancy rate of the coil in each of the slots. This reduces the size of the motor per unit of output.
An SC coil of a stator disclosed in the aforementioned document is a conductor segment (a coil segment) configured by two types of U-shaped conductive wires, each of which includes two legs and a joint portion for joining the legs together. The SC coils are axially arranged in the corresponding slots, which are formed in a stator core. Each adjacent pair of the legs of the SC coils are then welded and joined to each other in a step performed later, thus forming a coil that extends continuously in a circumferential direction.
Each one of the two types of the U-shaped conductive wires, which configure every segment conductor, is formed by bending a conductive wire in a U shape about a middle portion of the conductive wire. In other words, the arcuately bent portion corresponds to the joint portion and the portions extended from the opposite ends of the joint portion correspond to the legs. Then, the segment conductor is formed by arranging the second U-shaped conductive wire in the space formed by the inner surface of the joint portion and the inner surfaces of the legs of the first U-shaped conductive wire.
As has been described, the segment conductor is configured by the first U-shaped conductive wire wrapped around the second U-shaped conductive wire. Accordingly, the segment conductor has a laminated structure in which the joint portion of the first U-shaped conductive wire and the joint portion of the second U-shaped conductive wire are laminated with each other in the axial direction. As a result, a coil end becomes axially projected by the amount corresponding to the laminated joint portions of the first and second U-shaped conductive wires. This increases the total axial length of the stator and thus the size of the motor.